Walter koqowski aitd waltes gbossee



W. ROGOWSKH ET AL,

GLOWING CATHODE OSC'ILLOGRAPH Filed Nov. '7, 192% J2 uen fors:

l atented Nov. 2, l fi.

fiTATES PATENT @FFHCE.

GLOWING-CATHODE OSCILLOGBAPH.

application filed. November 7, 1925, Serial No. 67,687, and. in Germany December 20, 1923.

In electron-discharge tubes with a glowing cathode it is generally of no importance which way and at what point the electrons reach thev anode. It is only necessary that they reach the anode at all. In Brauns tubes with glowing cathodes it is desirable that the electrons emitted by the filaments are all concentrated as much as possible on one single point of the fluorescent screen, photographic plate, or any other suitable means designed to display the deflection of the rays. This concentration generally encounters diificulties and in order to overcome these difficulties it has been customary to first pass electrons emitted by the filament through a small opening of a fiat diaphragm and to concentrate them only then on the desired point by a longitudinal magnetic field established in rear of the said diaphragm. However, this process involves the disadvantage that only a comparatively small part of the electrons emitted by the filament penetrates through the diaphragm opening, because the electric lines of force proceeding from the glowing cathode distribute on the entire surface of the fiat diaphragm, thus forming a more or less divergent field. Therefore, the electrons generally flow directly on the metal of the diaphragm and only exceptionally through its opening.

The present invention has for its object to concentrate. the electrons emitted by the glowing cathode on a point as small as possible. Tt resides in that, by a suitable arrangement and shape of main and auxiliary electrodes and of diaphragms and by a suitable selection of the potential between the electrodes, there is produced an electric field which converges from the glowing cathode towards one point. This point is formed as an opening in a diaphragm so that the electrons flow in a large number through this opening and may be concentrated again in rear of the diaphragm by a longitudinal magnetic field in a sharp point.

The convergent field is formed by the field of a bored cone which is arranged as an anode opposite the filament and auxiliary electrodes. The apex of the cone is either sharp or more or less rounded off.

The invention will now be described with reference to the accompanying drawing in which Figs. 1, 2, 3 and 4. show elevations, partly in section, of four embodiments of a glowing-cathode oscillograph according to the invention.

This device in which the electrons are concentrated in ,one point, is preferably called glowing-cathode oscillpgraph with an electron-focus. Fig. l is a simple form of a tube accord- 1ng to the invention. a is the anode which is formed by a diaphragm consisting of a cone with abore b opposite of which is arranged the glowing cathode c. If there exists an acceleration potential between the cone and the cathode, the cone produces a convergent electrical field, so that a large part of the electrons is caused to flow through the bore of the cone.

Although there is already obtained with the arrangement according to Fig. 1 a considerably higher efficiency than with tubes having the ordinary fiat diaphragm, yet this efficiency may be further increased by providing the filament with a metallic auxiliary electrode a, as shown in Fig. 2 and known in Bontgen tubes, and by suitably adjusting the distance between the cone a and the auxiliary electrode d. It is necessary to prevent the electric lines of force proceeding from the filament itself ending on the metal surface of the enlarged portion of the cone-shaped diaphragm, because the electrons which might follow these lines of force would certainly not flow through the openings of the diaphragm, and would therefore become lost. 0n the contrary, all lines of force attackingthe filament should be caused to take their path through the opening of the diaphragm and to end in the bore or on the rear side of the same. The fulfilling of this requirement is apparently facilitated by surrounding the filament with a metallic auxiliary electrode such as (l. The most favorable proportion of the diaphragm opening, of the space between the auxiliary electrode and the diaphragm and of the dimension of the filament may be determined by tests.

The finer the opening of the diaphragm and the more extensive the filament is made, the more difficult will it be to guide the lines of force attacking the filament through the diaphragm opening to the rear side of the diaphragm. This difficulty may be overcome by surrounding the filament in a wellknown manner with a narrow metallic sleeve 6 as shown in Fig. 3. It will be understood that by making the sleeve of a suitable depth the aforesaid requirement may always be fulfilled and the produced electrons caused to pass through the diaphragm opening.

If the sleeve is surrounded by a metallic auxiliary electrode and variable potentials are applied to the latter and the sleeve with respect to the diaphragm, as shown in Fig. 4, the (proportion between the lines of force emitte by the filament and those emitted by the auxiliary electrodes ma be readily V changed. It is thereby rendere possible to establish the best efiicier'icy of a certain tube in a simple manner. The most favorable distances, shape and dimensions of all electrodes and the most favorable potentials between them are to be determined by tests.

f is a fluorescent screen.

As a matter of course, the difiiculties of the concentration are reduced by keeping the glowing surface of the cathode as small as possible.

The described arrangements of electrodes are not only effective if they are placed near the cathode, but also if they are disposed anywhere in the path of the electrons.

Having thus described our invention what we claim as new and desire to secure by Letters-Patent, is i 1. Inc. glowing-cathode oscillograph, an anode in the form of a hollow metallic cone arranged opposite the glowing cathode with its apex directed toward the cathode.

2. In a glowing-cathode oscillograph, an anode in the form of a hollow metalllc cone directed with its apex toward the cathode, and a metallic auxiliary electrode surrounding the cathode and held on any constant potential.

3. In a glowing-cathode oscillograph, an anode in the form of a metallic cone arranged opposite the cathode, a metallic sleeve surrounding the cathode, a metallic auxiliary electrode surrounding the sleeve, and external means for holding the cathode, the sleeve and the auxiliary electrode on any constant potentials with respect to the anode, the positive pole of all potentials lying at the anode.

In testimony whereof we have names to this specification.

WALTER ROGOWSKI. WALTER GBossER.

signed our 

